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  • 1
    Keywords: brain ; RECEPTOR ; CELLS ; Germany ; NETWORKS ; SYSTEM ; TOOL ; DISTINCT ; PROTEIN ; PROTEINS ; TRANSDUCTION ; COMPLEX ; MESSENGER-RNA ; RAT ; signal transduction ; MEMBRANE ; SIGNAL-TRANSDUCTION ; mass spectrometry ; MASS-SPECTROMETRY ; CHROMATOGRAPHY ; PROTEOMIC ANALYSIS ; glutathione-S-transferase ; BINDING PROTEIN ; signaling ; molecular ; NEURONS ; analysis ; cilia ; ENGLAND ; XENOBIOTIC-METABOLIZING ENZYMES ; affinity chromatography ; calcium-calmodulin ; CHEMOSENSORY CILIA ; NUCLEOTIDE-GATED CHANNEL ; olfaction ; olfactory receptor neurons ; PHOSPHOLIPID-BINDING ; SENSORY NEURONS
    Abstract: The olfactory neuroepithelium represents a unique interface between the brain and the external environment. Olfactory function comprises a distinct set of molecular tasks: sensory signal transduction, cytoprotection and adult neurogenesis. A multitude of biochemical studies has revealed the central role of Ca2+ signaling in the function of olfactory receptor neurons (ORNs). We set out to establish Ca2+-dependent signaling networks in ORN cilia by proteomic analysis. We subjected a ciliary membrane preparation to Ca2+/calmodulin-affinity chromatography using mild detergent conditions in order to maintain functional protein complexes involved in olfactory Ca2+ signaling. Thus, calmodulin serves as a valuable tool to gain access to novel Ca2+-regulated protein complexes. Tandem mass spectrometry (nanoscale liquid-chromatography-electrospray injection) identified 123 distinct proteins. Ninety-seven proteins (79%) could be assigned to specific olfactory functions, including 32 to sensory signal transduction and 40 to cytoprotection. We point out novel perspectives for research on the Ca2+-signaling networks in the olfactory system of the rat. (C) 2007 IBRO. Published by Elsevier Ltd. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 18155848
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  • 2
    Keywords: INHIBITION ; PROTEIN ; ACTIVATION ; MECHANISM ; BINDING ; SUBUNIT ; MODULATION ; CALCIUM ; ion channels ; STOICHIOMETRY ; olfactory receptor neurons ; CA2+-DEPENDENT INTERACTIONS ; CNG CHANNELS ; ODOR ADAPTATION ; TERMINAL REGIONS
    Abstract: Cyclic nucleotide-gated (CNG) channels operate as transduction channels in photoreceptors and olfactory receptor neurons. Direct binding of cGMP or cAMP opens these channels which conduct a mixture of monovalent cations and Ca2+. Upon activation, CNG channels generate intracellular Ca2+ signals that play pivotal roles in the transduction cascades of the visual and olfactory systems. Channel activity is controlled by negative feedback mechanisms that involve Ca2+-calmodulin, for which all CNG channels possess binding sites. Here we compare the binding properties of the two LQ-type calmodulin binding sites, both of which are thought to be involved in channel regulation. They reside on the isoforms CNGB1 and CNGA4. The CNGB1 subunit is present in rod photoreceptors and olfactory receptor neurons. The CNGA4 subunit is only expressed in olfactory receptor neurons, and there are conflicting results as to its role in calmodulin-mediated feedback inhibition. We examined the interaction of Ca2+-calmodulin with two recombinant proteins that encompass either of the two LQ sites. Comparing binding properties, we found that the LQ site of CNGB1 binds Ca2+-calmodulin at 10-fold lower Ca2+ levels than the LQ site of CNGA4. Our data provide biochemical evidence against a contribution of CNGA4 to feedback inhibition. In accordance with previous work on photoreceptor CNG channels, our results indicate that feedback control is the exclusive role of the B-subunits in photoreceptors and olfactory receptor neurons
    Type of Publication: Journal article published
    PubMed ID: 21413724
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  • 3
    Keywords: RECEPTOR ; EXPRESSION ; Germany ; INFORMATION ; SUPPORT ; TOOL ; SITE ; PROTEIN ; PROTEINS ; TRANSDUCTION ; MECHANISM ; primary ; RAT ; mechanisms ; signal transduction ; MEMBRANE ; SIGNAL-TRANSDUCTION ; mass spectrometry ; MASS-SPECTROMETRY ; LOCALIZATION ; RECEPTORS ; FOOD ; protein expression ; PROTEOMIC ANALYSIS ; POLYACRYLAMIDE GELS ; NEURONS ; analysis ; TECHNOLOGY ; EPITHELIUM ; ENGLAND ; enzymatic ; XENOBIOTIC-METABOLIZING ENZYMES ; CHEMOSENSORY CILIA ; NUCLEOTIDE-GATED CHANNEL ; olfactory receptor neurons ; ODORANT RECEPTORS ; SENSITIVE ADENYLATE-CYCLASE ; sensory cilia
    Abstract: The cilia of mammalian olfactory receptor neurons (ORNs) represent the sensory interface that is exposed to the air within the nasal cavity. The cilia are the site where odorants bind to specific receptors and initiate olfactory transduction that leads to excitation of the neuron. This process involves a multitude of ciliary proteins that mediate chemoelectrical transduction, amplification, and adaptation of the primary sensory signal. Many of these proteins were initially identified by their enzymatic activities using a membrane protein preparation from olfactory cilia. This so-called "calcium-shock" preparation is a versatile tool for the exploration of protein expression, enzyme kinetics, regulatory mechanisms, and ciliary development. To support such studies, we present a first proteomic analysis of this membrane preparation. We subjected the cilia preparation to liquid chromatography-electrospray ionisation (LC-ESI-MS/MS) tandem mass spectrometry and identified 268 proteins, of which 49% are membrane proteins. A detailed analysis of their cellular and subcellular localization showed that the cilia preparation obtained by calcium shock not only is highly enriched in ORN proteins but also contains a significant amount of nonciliary material. Although our proteomic study does not identify the entire set of ciliary and nonciliary proteins, it provides the first estimate of the purity of the calcium-shock preparation and provides valuable biochemical information for further research
    Type of Publication: Journal article published
    PubMed ID: 18032372
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